Towns along Western Australia’s coastline are among the most susceptible to climate change in the world with the areas of Mandurah, Busselton, Rockingham and Bunbury under particular threat of flooding and coastal erosion, a new Climate Commission report reveals.
The report estimates between 18,700 and 28,900 residential buildings – worth up to $7.7 billion - are at risk of inundation due to rising sea levels.
A further 2100 commercial buildings – more than in all other states – and up to 9100 kilometres of roadway along the coast of the state are also under threat.
“A sea-level rise of 50 centimetres will lead to very large increases in the frequency of coastal flooding; flooding that is currently considered a one-in-100 year event would occur every year in most parts of WA and even more frequently in Perth,” the report says.
“Flooding events are likely to damage cities, towns and the supporting infrastructure in low-lying coastal areas and will lead to erosion of sandy beaches.”
Sea levels along the WA west coast have been rising about double the global average since 1990, at between 7.1 millimetres and 7.4 millimetres per year, according to the commission.
Fremantle already has seen a 20 centimetre rise in the sea level since the late 1800s, which has caused a three-fold increase in recorded flooding.
Average global sea levels are projected to increase by a further 0.5-1.0 metres this century.
The commission also identified the state’s South West as an area particularly vulnerable to climate change, which had contributed to a significant decline in rainfall.
Climate Commissioner Professor Will Steffen said declining rainfall and higher temperatures would have serious implications for agriculture and urban water supplies in the South West.
“We are more certain of the climate change risks for water resources for south-western WA than any other part of Australia,” he said.
“Over the last 40 years we’ve watched the south-west of the state become markedly drier with significant impacts for agriculture and urban water supplies.”
A 15 per cent drop in Perth’s rainfall would equate to a 45 per cent decline in overflow to the city’s dams, reducing water supplies.
Perth’s average dam flow rate has halved since 1975 to just 13 gigalitres for 2013, compared to an average 177 gigalitres between 1975-2000 period.
The state government already has recognised the severity of the problem, announcing last month that it would immediately double the Southern Seawater Desalination Plant at Binningup, north of Bunbury.
The drying trend also has important consequences for the Wheatbelt, the commission says.
The growing season already has become shorter and drier in the northeastern part of the area and yields are expected to decline another 30 per cent by 2050.
The commission recommended urgent action as the state’s globally recognised coral reefs and biodiversity were already significantly affected.
The state’s tourism industry - its second most important industry - faces significant long-term risks from climate change, with the Ningaloo Reef off the state’s north-west coast already experiencing coral bleaching and about 75 per cent of WA native vegetation cleared for agriculture and human settlements.
Professor Steffens said without tough and rapid action there was a significant risk that climate change would undermine the society’s prosperity, health, stability and way of life.
“Failing to take sufficient action today entails potentially huge risks to our environment, economy, society and way of life into the future,” the report says.
He recommended decarbonising the economy and moving to clean energy sources by 2050, which would require carbon emissions peaking within the next few years and then significantly declining.
“The risks have never been clearer and the case for action has never been more urgent,” Professor Steffen said.
“This is the critical decade. The decisions we make this decade will determine the severity of climate change impacts our children and grandchildren suffer.”
The commission highlighted WA’s high potential for renewable energy, with some of the best wind and solar opportunities in Australia.
The Climate Commission, including climate commissioners Tim Flannery, Lesley Hughes, Will Steffen and Susannah Elliot, will this week tour south-western WA to meet with community leaders and attend two town hall forums in Bunbury and Perth.
